WOW! You have a very precise method for calculating when potatoes are ready. I use a much less sophisticated method. Sweet potatoes are supposed to be ready 130-170 days after planting. I mark 150 days on my garden calendar to check them, and I put a label in the pot with the planting date and expected date of maturity. As it turns out everything here takes a lot longer then what is expected. I dig into the container and feel the size of the potatoes. If they seem about right I pull them up. Since we don't get a winter here, the vines will not die down, so that is not a reliable sign. Sweet potatoes can be invasive, so it works better to keep them in large containers. It also makes it easier to harvest since I have hard clay soil. Thankfully, I don't have to move the containers much.
If I plant the right varieties, I can also eat the leaves